The present invention relates to a semiconductor device and a method of manufacturing the same.
In recent years, in keeping with a trend of implementing the semiconductor device in a miniaturized structure, there has arisen the requirement that the gate of a transistor be realized in a length of 0.15 μm with the film thickness of the gate insulation film being decreased to less than 2 nm when silicon oxide (SiO2) is employed for the gate insulation film. In this conjunction, it is noted that such thickness of the gate insulation film as mentioned above will give rise to occurrence of a tunnel current of unignorable magnitude. To cope with this problem, it has been attempted to increase the physical film thickness while maintaining the desired dielectric characteristic by using an insulation material exhibiting higher dielectric constant (or permittivity) than SiO2.
As a candidate for such high dielectric constant material, there may be mentioned titanium oxide, as is reported in the collection of lecture reprints of “THE 1999 INTERNATIONAL CONFERENCE ON SOLID STATE DEVICES AND MATERIALS”, pp. 164-165.
However, in the present state of the art, when the semiconductor device is formed by using titanium oxide for the gate insulation film in actuality, a leak current will flow through the gate insulation film of titanium oxide, degrading the reliability of the semiconductor device. Such being the circumstances, there exists a demand for practical implementation of the semiconductor device in which the occurrence of the leak current is suppressed by increasing the physical film thickness while maintaining the dielectric characteristic.